Six months after the first revelations appeared in The Washington Post and Britain’s Guardian newspaper, Snowden agreed to reflect at length on the roots and repercussions of his choice. He was relaxed and animated over two days of nearly unbroken conversation, fueled by burgers, pasta, ice cream and Russian pastry.

Snowden offered vignettes from his intelligence career and from his recent life as “an indoor cat” in Russia. But he consistently steered the conversation back to surveillance, democracy and the meaning of the documents he exposed.

“For me, in terms of personal satisfaction, the mission’s already accomplished,” he said. “I already won. As soon as the journalists were able to work, everything that I had been trying to do was validated. Because, remember, I didn’t want to change society. I wanted to give society a chance to determine if it should change itself.”

“All I wanted was for the public to be able to have a say in how they are governed,” he said. “That is a milestone we left a long time ago. Right now, all we are looking at are stretch goals.”

Snowden is an orderly thinker, with an engineer’s approach to problem-solving. He had come to believe that a dangerous machine of mass surveillance was growing unchecked. Closed-door oversight by Congress and the Foreign Intelligence Surveillance Court was a “graveyard of judgment,” he said, manipulated by the agency it was supposed to keep in check. Classification rules erected walls to prevent public debate.

Toppling those walls would be a spectacular act of transgression against the norms that prevailed inside them. Someone would have to bypass security, extract the secrets, make undetected contact with journalists and provide them with enough proof to tell the stories.

The NSA’s business is “information dominance,” the use of other people’s secrets to shape events. At 29, Snowden upended the agency on its own turf.